[Eeglablist] Importing data from Brain Vision Analyzer

[Mich Spape]

Hi Katia,
We also use BrainProducts amps and I worked for a while with Brain Vision
Analyzer - it's a nice product. However, you probably mean that your .eeg,
.vmrk, and .vhdr are Brain Vision Recorder files, which is what you normally
get with such amplifiers. If so, you can edit the .vhdr file with a text
editor to see what kind of settings were applied in the very early
preprocessing, such as the software filters. 
However, you can also save BVA type of files from within Brain Vision
Analyzer, but these come with .ehst2 and .hfinf2 that have the processing
steps in there. BVA basically works by keeping these together with the raw
data, saving parts of the preprocessing steps in such files. It's possible
that your supervisor thought you'd get pre-processed data when they provided
the raw data. If that was the idea, they might want to look in the workspace
of BVA: there are specific directories for raw, history, and exported data.
In order to work with pre-processed data, the easiest way is to put a
generic data export at the part of the processing tree that is appropriate
for where they want you to start from. if I remember correctly, however,
these will have header files that will say something like 'Data created from
history path: /Raw Data/Filters/MarkerAddMIr/MarkersTranslate/Raw Data
Inspection/seg/DC Detrend/Baseline Correction/arfinal/segexp0exp1/'' (and so
on), so if any preprocessing steps were executed and this person documented
it reasonably well, you might still find out. 

TL;DR: I would guess they are raw brain vision recorder files, check by
editing the header file, but do ask your supervisor.

Best,
Michiel Spape

// Senior researcher, Docent 
// Department of Psychology & Logopedics
// University of Helsinki


-----Original Message-----
From: eeglablist <eeglablist-bounces at sccn.ucsd.edu> On Behalf Of Katarzyna
Dudzikowska
Sent: 25 June 2020 14:42
To: eeglablist at sccn.ucsd.edu
Subject: [Eeglablist] Importing data from Brain Vision Analyzer

Dear all,

I am about to embark on my very first EEG data analysis project. I received
data from my supervisor who works with Brain Vision Analyzer, I have .eeg,
.vmrk and .vhdr files. I understand that .eeg is the actual recording, .vmrk
contains information about the events and .vhdr is the metadata file that I
have successfully used to import the datasets into EEGLAB using the bva-io
plugin.

My problem is that I simply do not know whether the data I have includes any
preprocessing steps or not, or how I can tell. Would .eeg data in principle
be raw data? Or is it possible that it does already include some artifact
rejection and/or channel interpolation that has been performed on this
dataset in Brain Vision Analyser? Is there any way to figure it out from the
data itself? It imports as a single, continuous epoch.

Originally I was meant to work with already preprocessed data, but it seems
that I have to carry it out somewhat differently for my research goals. Can
I safely undertake my own preprocessing steps on the data as I have it?

I'd be very grateful for some help figuring this out.

Best,
Katia
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